1. Field of the Invention
This invention relates generally to a device used in the interventional treatment of neurological disorders, and more particularly to a novel electrode-lead coupling assembly which mounts to a burr hole in a patient's skull and couples an implanted electrode to a lead which extends external to the skull to a powered signal generator.
2. Description of the Prior Art
The use of electrical stimulation of the brain for the purposes of alleviating pain and the treatment of other neurological afflictions has been utilized for a number of years, and in many instances has become the standard of care. The traditional technique comprises the implantation of a long flexible electrical lead through a burr hole in the patient's skull, and into electrical contact with the pathological section of the patient's brain. The flexible lead comprises a plurality of long helically wound wires encased in a elastomeric sheath. The distal end of the wire lead include electrical contacts and are placed in the brain. Once positioned, the lead is secured to the skull such that the internal portion is locked, and prevented from movements. The proximal end of the wire lead remain external to the skull, and is coupled to an extension connector which joins the electrical wires to an electrical generator.
As is clear from the delicacy of the surgical field, it is critical to utilize robust instruments and implants which are not easily broken, and which do not lend themselves easily to unwanted movements. In particular, there are two concerns which the surgeon has when utilizing traditional equipment. The first concern is related to the securing of the lead to the skull. More particularly, when an electrode lead is implanted, the position of the active tip is critical. The effects of the field generated by the electrical contacts is highly position dependent, and as a result, movement of the electrode after proper positioning can reduce or eliminate all effectiveness of the treatment. As it can be a very tedious process to find the appropriate location within the brain for the active tip, it is also critical that once the lead is situated, it should not be moved accidentally. If external portions of the lead are not secured, subsequent manipulations of the electrode leads can cause this unwanted movement.
One such device which is presently available in the art is illustrated in FIG. 1, and is described in U.S. Pat. No. 5,464,446. It comprises a first port member 22 which is cylindrical and seats in the burr hole formed in the patient's skull 24. The exterior lateral surface of the port includes a contoured circumferential flange portion 26 which is intended to form a seal with the inner lateral surface 28 of the burr hole. The upper portion of the port member includes an outwardly extending rim 30 which seats against the exterior surface of the skull 30 around the edge of the burr hole when the port is inserted fully in the burr hole. This upper contour is also designed to mate with a cap section 32. The central axis of the seating member 22 forms a channel through which the electrode 34 seats and can slide prior to being locked in place. The cap 32 has a pair of channels formed therein; a first 36 which extends axially along the same direction as the axial passage in the port member, and the second 38 which extends out radially along the undersurface. The cap 32 engages the upper contour (and requires a suture 40 to hold the members together) in such a way that the electrode lead is compressed and is thereby locked in place. The use of a suture to secure the electrode, even indirectly, is a considerable drawback as it is difficult to manipulate, not easily reversible, and does not provide a readily obvious means for ensuring that the lead is truly secured against movements when the external portion is manipulated during the remainder of the surgery. Also, the compression lock, as in the first example is not easily viewed as it happens under the cap member.
In co-pending application, U.S. Ser. No. 09/489,000, entitled "A Skull Mounted Electrode Lead Securing Assembly", assigned to the same assignee as the present invention, the present inventors have provided an invention which is an advance over the prior art in the field of securing the electrode lead to the skull. The specification of said application is hereby included fully, by reference.
The second concern which surgeons have regarding the presently available equipment is with regards to the electrical joining of the proximal end of the electrode lead to the extending cable which couples the electrode to the remote electrical signal generator. Unfortunately, because of the techniques and equipment used in implantation of the lead within the brain, the joining of the proximal end of the electrode to the extending cable occurs after the distal end of the electrode has been fully implanted and positioned, and the cannula has been removed. At this stage, damage to the proximal end of the electrode, even if such damage does not cause the distal end to move, will require the removal of the implanted lead. Removal of the lead requires that the entire implantation procedure to be repeated (a process which can take several hours). The presently available extension cables and the coupling means for connecting the proximal end of the lead thereto are prone to causing damage to the proximal end of the implanted electrode.
One alternative solution to this concern is to provide a more robust coupling end to the implanted lead. This alternative requires several modifications of equipment used during the implantation steps. The present inventors have provided for several such modifications, including co-pending applications U.S. Ser. Nos. 09/489,004, 09/489,003 and 09/489,002 entitled "A Helically Slotted Cannula", "An Axially Separable Cannula", "A Coupling Mechanism for Connecting A Deep Brain Stimulation Lead to an Electrical Extension Cable", respectively, each of which is assigned to the assignees of the present invention, the specifications of each being incorporated herein, fully, by reference.
The solution of the present invention is related, instead, to providing a more reliable coupling for the electrode which reduces the potential for damage and simultaneously prevents the implanted portion of the electrode from being moved once properly positioned.
The objects of the present invention are, therefore, clearly to provide an electrode securing assembly which reliably, easily, reversibly, and obviously locks an electrode lead to the skull, and most importantly, prevents the unwanted movement of the implanted portion of a deep brain stimulation lead during the manipulation of the external portion after the active internal tip has been properly positioned.
Simultaneously, it is an object of the present invention to provide an assembly which reliably and non-destructively couples the implanted electrode lead to the extension lead.
In addition, it is also an object of the present invention to provide a mechanism which is easily manipulated by the surgeon under the conditions of the surgical field.